In a typical cellular network, also referred to as a wireless communication system, User Equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks (CNs).
A user equipment is a mobile terminal or mobile station by which a subscriber may access services offered by an operator's core network and services outside operator's network to which the operator's RAN and CN provide access. The user equipments may be for example communication devices such as mobile telephones, cellular telephones, or laptops with wireless capability. The user equipments may be portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another mobile station or a server. In the following, the term user equipment is used.
User equipments are enabled to communicate wirelessly in the cellular network. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between the user equipment and a server via the radio access network and possibly one or more core networks, comprised within the cellular network.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g. a Radio Base Station (RBS), which in some radio access networks is also called evolved NodeB (eNB), NodeB, B node, base station or Base Transceiver Station (BTS), depending on the technology and terminology used. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g. by landlines or microwave, to a Radio Network Controller (RNC), as in 3rd Generation (3G), i.e. Wideband Code Division Multiple Access (WCDMA). The radio network controller supervises and coordinates various activities of the plural base stations connected thereto. In 2nd Generation (2G), i.e. Global System for Mobile Communications (GSM), the base stations are connected to a Base Station Controller (BSC). The network controllers are typically connected to one or more core networks.
A relay node (RN), or just simply relay, in a wireless communication network is used to receive and re-transmit/forward signals intended for mobile stations, in a mobile network, i.e. for user equipments in a communications network. A mobile station may be referred to as user equipment in Third Generation Partnership Project (3GPP) terminology. A number of user equipments may be served by a single relay node. A key objective of the relay node is to enhance the radio access coverage in both the UpLink (UL), i.e. user equipment to base station transmissions, and DownLink (DL), i.e. base station to user equipment transmissions. A relay node may be positioned between a base station and a user equipment so that transmissions between the base station, referred to as the donor base station, and the user equipment are relayed by the relay node.
The relay node connectivity or architecture in Long Term Evolution (LTE) networks is described in 3GPP. In LTE the relay connectivity or architecture comprises:                relay node connected wirelessly to a donor cell of a donor eNode B (DeNB) via the radio backhaul link, and        user equipments connect to the relay node via the radio access link.        
FIG. 1 depicts a communications network 100 illustrating the connection between different nodes when a relay node 103 is used, i.e. it illustrates a single hope relay architecture in the communications network 100. The relay node 103 is connected wirelessly to a donor cell of a donor eNode B105 via a radio backhaul link 104, and UEs 107 are connected to the relay node 103 via a radio access link 108. In LTE, the radio backhaul link 104, i.e. DeNB-relay node link, and the radio access link 108, i.e. relay node-UE link, are termed the Un and Uu interfaces, respectively. The relay architecture shown in FIG. 1, illustrates that the eNB 105 connects to the LTE Evolved Packet Core (EPC) 110.
The relay node 103 connects to the DeNB 105 via the Un interface using the same radio protocols and procedures as used by the UE 107 for establishing a connection to an eNB 105. During the Radio Resource Control (RRC) connection setup phase, the relay node103 signals an RN indicator to the DeNB 105. The RRC is a protocol which handles the control plane signaling of Layer 3 between the UEs 107 and the Universal Terrestrial Radio Access Network (UTRAN). Based on the received RN indicator, the DeNB 105 executes certain functions which are specific to the relay operation. For instance the DeNB 105 selects the relevant core network node, i.e. a Mobility Management Entity (MME) in LTE, which is capable of supporting the relay functionality.
As a general matter, the relay node 103 may be fixed or wireless. Furthermore, a wireless relay node 103 may be implemented as a standalone mobile relay or a wireless terminal. Typically a mobile relay may be deployed in a movable vehicle such as a bus, train, ferry etc, primarily to serve UEs 107 in the movable vehicle, but also to serve UEs 107 in surrounding areas. relay nodes 103 may therefore be distinguished as being of different types.
However, despite the existence of different variants or types of relay nodes 103, the donor node 105 is unable to distinguish between these different types. Because of this, procedures specific to a particular relay type may not be executed, or are executed unnecessarily. As a consequence, some of the relay functions may not be operable, and the full potential of the relays 103 may not be utilized. Furthermore there will not be any motivation to deploy relays of different types, which are beneficial in different environments and scenarios.
Spectrum Usage in Relays
With respect to a relay nodes 103 usage of radio spectrum, an relay node 103 may be classified into the following two categories: in-band relay and out-band relay. For an in-band relay 103, the backhaul link 104 and the access link 108 operate using the same carrier frequency. Typically, therefore, communication over the backhaul 104 and access links 108 takes place in a time division manner. However, in principle, simultaneous operation over the two links may nonetheless be achieved with sufficient isolation between the access 198 and backhaul links 104, e.g. by virtue of directive transmission. For an out-band relay, the backhaul link 104 and the access link 108 operate using different carrier frequencies.
Carrier Aggregation (CA) in Relays
Carrier aggregation is used to aggregate two or more component carriers for supporting high data rate transmissions over a wide bandwidth, e.g. up to a 100 Mega Hertz (MHz) for a single UE 107 in LTE. CA may be used in the downlink, uplink or in both direction. Carrier aggregation is also referred to as, e.g., interchangeably called, “a multi-carrier system”, “multi-carrier operation”, “multi-carrier” transmission and/or reception. Typically the component carriers in carrier aggregation belong to the same technology, e.g., all carriers are WCDMA carriers, or all carriers are LTE carriers. However carrier aggregation between carriers of different technologies is also possible to increase throughput.
CA may also be used in a relay environment to increase the data rate over the backhaul 104 and/or access link(s) 108. Furthermore, carrier aggregation may be used in both in band and out band relays. The same relay 103 may also be configured to operate in the baseline, i.e., legacy, single carrier operating mode.
Relay Deployment Scenarios
Typically more than one relay node 103 connects to the same donor base station 105. The relay nodes 103 are generally deployed in the coverage area of the donor cell, which is served by the donor node e.g. donor eNode B. As the primary function of the relay node 103 is to improve coverage, both outdoor and indoor relay node deployment scenarios are beneficial. An outdoor relay node 103 may be used for cell edge coverage improvement. An indoor relay node 10 3 may be used for solving indoor dead spot and hot spot scenarios.
Furthermore when deployed outdoor or indoor the antennas used for the backhaul 104 and access links 108 may either be in the indoor or outdoor i.e. any combination is possible in principle. Also, different Multiple-Input Multiple-Output (MIMO) configurations may also be used in the access 108 and backhaul links 104. For example, a relay node 103 may be associated with 2 transmit and 2 receive antennas on the access links 108, and 4 transmit and 4 receive antennas on the backhaul link 104 respectively.
In FIG. 2, the relay node 103 is deployed outdoors in a communications network 100. Further, all the relay antennas for the transmission/reception of signals over the backhaul link Un 104 to the eNB 105 and access link Uu 108 to the user equipment 107 are located outdoors. The outdoor relay 103 serves outdoor user equipments 107a, as well as indoor user equipments 107b. 
In FIG. 3, the relay node 103 is deployed indoors in a communications network 100. Further, all the relay antennas for the transmission/reception of signals over the backhaul link Un 104 to the eNB 105 and the access link Uu 108 to the user equipment 107 are located indoors. The indoor relay node 103 primarily serves indoor user equipments 107.
In FIG. 4, the relay node 103 is deployed indoors in a communications network 100. But the relay antennas for the transmission/reception of signals over the backhaul link Un 104 to the eNB 105 are located outdoors, while the antennas for the access link Uu 108 to the user equipment 107 are located indoors. This type of relay deployment is also called a Thru-wall or through-wall deployment, and is meant to primarily serve indoor user equipments 107. The use of outdoor backhaul antennas results in improved backhaul link quality e.g. compared to the purely indoor deployment of FIG. 2.
Multi-Standard Radio (MSR) Relay
A relay node 103 may also comprise a Multi-Standard Radio (MSR). A MSR relay node 103 comprises common Radio Frequency (RF) components, e.g. power amplifiers, RF filters, which may be used to operate:                (1) more than one Radio Access Technology (RAT); or        (2) more than one carrier within the same RAT.        
More specifically, the MSR relay node 103 may also be termed as Multi-Carrier Multi-Standard Radio (MC-MSR) base station due to the fact that it may comprise a single RAT with more than one carrier.
Hence a single RAT MSR is a special case of an MSR. Furthermore a special case of MSR may also comprise a relay node 103 that supports a single carrier within a RAT, i.e. single carrier single RAT MSR relay 103. The MSR relay 103 may be Frequency-division duplexing (FDD) or Time-Division Duplex (TDD). Examples of RATs supported in FDD MSR relay are: LTE FDD, UTRA FDD and GSM/GERAN. Another example is: LTE FDD and 3GPP2 Code Division Multiple Access (CDMA) technologies, e.g. CDMA2000 and High Rate Packet Data (HRPD). Examples of RATs supported in FDD MSR relay are: LTE TDD and UTRA TDD.
The carriers within FDD or TDD MSR relay 103 may be contiguous or non-contiguous. Furthermore such relay 103 may be used in a single hop or in a multiple hop relay system.
Other Types of Relay Nodes
Relay nodes 103 may also be classified into other types of categories. The most fundamental classification of relays 103 is based on whether the relay 103 is fixed or movable:                Fixed relay: A fixed relay is always fixed in the sense that its geographical location remains unchanged.        Movable relay: A moveable relay may move or remain stationary depending upon the mobility state of the object carrying the relay. Hence mobility is the major characteristic of the movable relay, because its geographical location may change. However other characteristics may be very similar to those of the fixed relay. For instance similar to the fixed relay, the movable relay also has backhaul and access links, and may also be an in band or an out band.        
A movable relay may further be classified into sub-categories. Non-limiting examples of the sub-categories of movable relays are                Dedicated mobile relays: A dedicated mobile relay may be installed, for example, on a movable vehicle such as in a bus, train, boat etc to primarily serve the users inside the vehicle. However users outside the vehicle may also be served. This type of relay may be under the control of an operator or may be owned and managed by the subscriber or private owner.        Wireless terminals that act as a relay: Wireless terminals that act as a relay may be normal UEs or mobile terminals that are able to perform the relaying function.        Dedicated wireless terminal relays: Dedicated wireless terminal relays may comprise dedicated wireless terminal such as handheld wireless devices that perform relaying features to serve other users or terminals.        
As stated in earlier there are different variants or types of relay nodes 103, and not all procedures specific to a particular relay type may be executed. Some of the relay functions may not be operable and the full potential of the relays 103 may not be utilized.